There are a lot a builders struggling with tournament aircraft and course completion. I figured I'd throw out my two cents on the subject.

-You want to build an aircraft where the center of weight, thrust and lift points are very close to eachother. Just remeber that mass must be at least slightly forward of lift or the plane will be uncontrollable. Just remember, these values are expressed as moments, so the farther the weight is forward of lift, the more torque required to pitch up which will slow performance.

-All lifting and control surfaces must very exaggersted and large. This creates a few issues because large wings don't like to go fast and stay attatched, also large wings slow roll and pitch properties. One solution is stacking smaller wings (i.e. biplane wings and hor-stabs). This allows the aircraft to produce tons of lift and control input without sacrificing agility. Think of it as the opposite of increasing mass without increasing serface area, terminal velocity increases. You can effectively increase lift without increasing prasitic wing drag.

-Keep it simple stupid ;) The more complicated the aircraft is the more trouble the AI will have controlling it. Powerful engines and simple construction, that's the ticket. Also, check the race, if you don't need to takeoff get rid of those wheels and don't carry around even one extra liter of fuel.

-Test, test and test again. Test your aircraft under AI control... a lot... and make small adjustments until you start completing the course. Then test some more while making even smaller adjustments until you see the performance you are looking for. You'll be blown away by how much small changes will change performance.

-Lastly, look at what other people are building and cultivate some ideas. Low hanging fruit is all over the site, just make sure you build from scratch or it won't be accepted in a tourny. On this same note, all you skilled builders/racers should be offering whatever help you can; this is a collaborative website that should be fun.

I built this for Shark Tooth but I'll be running a my Reef Skimmyr because it's more consistant:
https://www.simpleplanes.com/a/eGmg6O/PY-T44-Reef-Walker